Debris-free perforating gun



y 1961 L. D. MEDDICK 2,986,089

DEBRIS-FREE PERFORATING GUN Filed Jan. 9, 1956 4 Sheets-Sheet 1 a j i /0 AOAQQfl/IV D. MEQO/CZ IN VEN TOR.

y 0, 1961 D. MEDDICK 2,986,089

DEBRIS-FREE PERFORATING GUN Filed Jan. 9, 1956 4 Sheets-Sheet 2 4022mm 0, MEDD/CZ IN V EN TOR.

May 30, 1961 L. D. MEDDICK 2,986,089

DEBRIS-FREE PERFORATING GUN Filed Jan. 9, 1956 4 Sheets-Sheet 5 LOEQQ/A D. A/EOD/CZ INVENTOR.

May 30, 1961 D. MEDDICK DEBRIS-FREE PERFORATING GUN 4 Sheets-Sheet 4 Filed Jan. 9, 1956 fie. J1.

Suva? will il/ff'llffllld LT IN V EN TOR.

47' TOR/V54 DEBRIS-FREE PERFORATING GUN Lorrain D. Meddick, Whittier, Califi, assignor, by mesne assignments, to Borg-Warner Corporation, Vernon, Calif., a corporation of Illinois Filed Jan. 9, 1956, Ser. No. 557,953

Claims. ((319102-20) This invention relates in general to well perforating and particularly to an improved form of gun adapted to be run through tubing to perforate a well or casing at desired points below such tubing.

The improved perforator gun has an array of shaped charges supported in a body retrievable intact from the borehole, with the charges positioned by means reduced to fine particles upon firing.

It has been conventional practice in the drilling of oil wells to drill first an earth borehole of relatively large diameter, in which a liner or casing, or a number of concentric casings reaching to different depths, are fixed permanently by suitable means such as cementing. After the casings have been properly positioned and set, perforation is accomplished at a predetermined level in the borehole to permit the entrance of oil from selected strata, following which a smaller tubing is introduced through the casings and set in the well at the desired depth. The well fluid, entering through the previously made perforations, flows or is pumped out of the well, as the condition requires, through the smaller tubing. The perforating process usually has been accomplished either with the aid of a so-called gun perforator, utilizing pro jectiles of the bullet type, or with a perforator device utilizing shaped explosive charges. It was formerly necessary to perform such perforating operations prior to insertion of the tubing, in the case of some wells, or to remove the tubing from the casing in the case of wells previously completed, in order to insert guns or perforator devices of adequate size and power.

More recently, techniques and equipment have been developed for accomplishing the perforating operations after insertion of the tubing in the well, and while it remains in place therein. This latter procedure has become known in the industry as a part of the technique called thrutubing completion, or permanent well completion, and may be accomplished either with suitable bullet perforators or with shaped charge devices. It is with improvements in the construction and use of shaped charge devices in connection with the art of thru-tubing completion operations that the present invention is principally concerned.

The practical and economic advantages of completion through tubing are considered by some to be so substantial that this method of operation has been quite widely adopted in the industry. The saving in time and labor resulting from eliminating the steps of pulling the tubing out of the well before perforating, and reinserting it thereafter, are readily apparent. However, it will be obvious that the size of the gun used, and the size of the shaped charge or solid projectile, is limited by the inside diameter of the tubing through which this equipment must be run. Various forms of guns have been used to secure the most effective penetration possible under such limiting conditions. For example, units have been employed having rigid bodies confining the charges and directing them properly. These units have been made extremely strong in order to withstand the explosive effects, so that 2,986,089 Patented May 30, 1961 the guns might be retrieved and reused. Guns of this type have not been uniformly successful, however, because it has been found impossible to prevent expansion and deformation such as to render them unusable after only a relatively short period of service. If made sufiiciently rigid to avoid this difficulty, they have a tendency to blow up in the well and damage the casing. At the other extreme, guns have been used of the expendable type; that is, a minimum of supporting metal has been employed in order to permit carrying the largest possible explosive charge. These guns partially disintegrate at the time of firing, but troublesome fragments may be left.

In either case, fragments remain in the well, and may interfere with subsequent operations, unless difficult and expensive cleanout operations such as fishing or bailing are employed to remove the unwanted material before the well is finally completed. Efforts to produce a gun having suflicient rigidity to hold the charges in proper alignment for ready handling both at the surface and in the well bore, yet which would not leave undesired material in I the borehole after the charges have been fired, have hitherto been unsuccessful.

The object of the invention is, therefore, primarily to provide improvements in the means for gun perforating through tubing in wells.

Another object is to provide a thru-tubing perforating gun which may be reused repeatedly.

A further object is to provide a form of perforating gun able to utilize the maximum size of shaped charges which can pass through a particular tubing and yet allow the gun to be retrievable for reuse.

Another object is to provide a gun capable of carrying a plurality of charges of maximum penetrating power but which will leave a minimum of debris in the hole.

A related object is to provide a gun in which such material as is left in the hole after firing is such as will not interfere with subsequent operations.

The present invention as illustrated in the several embodiments described hereafter, and which accomplished the foregoing objects, comprises perforator apparatus having a plurality of shaped charges disposed in spaced array and supported by a retrievable gun body which may be removed intact from the hole after the charges have been fired. The shaped charge units are of maximum size and penetrating power, but disintegrate completely so that no objectionable debris remains. The gun body a shown in the several embodiments illustrated in the figures is so arranged as to provide adequate support to maintain the charges in proper alignment, and yet is constructed in a form which will not be shattered by the explosion of the charges, and which will be readily retrievable.

In one embodiment the gun body is preferably constructed from round steel stock, with its upper end defining a cable head for engagement with a suitable cable and associated equipment for suspending the gun in the well and firing the charges. The lower end of the gun body forms a conventional bull plug, and the crosssection of the portion intermediate the ends takes the form of a segment of a circle. The charges are secured to the flat side of the segmental intermediate portion by disintegrable straps.

In another species of the invention the gun body is formed of high tensile strength members, which may be flexible steel cables. These cables are secured to the cable head, and hold together rigidly a plurality of shaped charges separated by spacers of a frangible material extremely strong in compression. A suitable material is the ceramic product commercially known by the trade name Steatite, which shatters to powder on the firing of the charges.

In another form, similar spacers are used, with the assembly held together by tension members consisting of strands of reinforced Primacord. These embodiments all have in common the characteristic that the frangible portions are reduced to fine particles by the explosion of the charges, and the large metal portions remain together thereafter and attached to the supporting means as a unit, so that no material is left in the hole to interfere with subsequent operations. In these assemblies the form of the spacers is such that they are self-locking about the supporting cables or Primacord. Hence no additional parts are required to maintain them in position, once they have been put together.

These and other objects, advantages and features of novelty will be apparent from a detailed study of the description hereinafter, together with the drawings, in which:

Figure l is a side elevational view of a gun embodying the invention;

Figure 2 is a cross-sectional view, taken as indicated by line 22 in Figure 1;

Figures 3a and 3b, taken together, show in elevation an alternative embodiment of the perforator gun of the invention;

Figures 4a, 4b and 4c, taken together, show, partially in longitudinal section and partially in elevation, additional details of construction of the embodiment of Figures 3a and 3b;

Figure 5 is a fragmentary elevational'view of additional details of the embodiment of Figures 3a and 3b, the view being taken as indicated by line 5-5 in Figure 3b;

Figure 6 is a cross-sectional view of the embodiment of Figures 3a, 3b and 5 taken as indicated by line 66 in Figure 5;

Figure 7 is a fragmentary, longitudinal sectional view, taken as indicated by line 7- -7 in Figure 6;

Figure 8 isa view, partially in section taken along the longitudinal axis of the upper portion of a gut] body, of another alternative embodiment of the invention in which the carrier cable is replaced by Primacord;

Figure 9 is a bottom view of the embodiment of Figure 8, taken as indicated by line 9--9 in that figure;

Figure 10. is a fragmentary view, partially in longitudinal section, showing a modification in the details of construction of the embodiment of the invention shown in Figure 8, wherein the suspension means consists of a Primacord loop knotted at the upper end; and

Figure 11 is a view similar to that of Figure 10. of another modification of the embodiment shown in that figure but in which the Primacord loop is knotted at its lower end.

It is to be understood that the invention is not limited to the precise form shown in the drawings, but may be embodied in a number of other equivalent forms.

In the embodiment illustrated in Figure 1, the gun assembly, generally indicated as 1, is seen in side elevation, with a cross-section taken as there indicated by the line 2--2, depicted in Figure 2. The gun assembly 1 is preferably formed of a high strength material such as steel which can readily resist the stresses set up therein by the firing of the explosive material. The gun I is formed with a central body portion 2, the cross-section of which is a segment of a circle of radius substantially the same as that of the upper and lower end portions described hereinafter. At its lower end the body portion 2 merges into a bull plug portion 3, which is terminally rounded to define a tip 4 adapted to guide the gun through the tubing. At its upper end the body 2 merges into a head portion '5 of radius the same as that of central body portion 2. A cable head connection 6.is adapted to receive and make firm attachment with the supporting cable 7. Cable 7 includes an insulated electrical conductor 8 which in turn makes connection to means disposed in the cable head 5 for igniting the charges. Cable head '6' is so. shaped that it may be readily engaged by conventional grappling equipment if desired. The central body portion 2 has an elongated flat surface 9, along which are disposed, at suitable spacing intervals a num ber of horizontally directed shaped charges 10. The charges 10 are held in position by means such as straps 11 suitably secured to the flat side of the central body portion 2, and adjacent charges are shown as headed in opposite directions. While the charges have been illus trated as being directed horizontally, it will be obvious that they might be mounted to fire at other angles as well, and in azimuthal directions other than those illustrated in the figures. Straps 11 are made of relatively thin, frangible material adapted to disintegrate when the charges are fired. A detonating fuse 12 is associated cooperatively with each of the charges 10.

The detonating fuse 12 may be that commercially known under the trademark Primacord, a detonating cord containing, for example, of PETN or RDX. PETN is an abbreviation for the compound pentaerythrite tetranitrate. RDX may be, for example, 98% cyclonite and 2% wax, cyclonite being an abbreviated term for the chemical compound cyclotrimethylene trinitramine. Other detonating means of similar properties may of course be used. The detonating fuse 12 is connected at its upper end to a conventional electric blasting or detonating cap 13 which is fired by electric current transmitted from the surface of the earth, under the control of an operator, through the conductor 8 to cable head 5.

Each of the individual shaped charges 10 has a cylindrical body portion 14 formed symmetrically about an axis of revolution, which in normal use will be supported horizontally in the well by the gun I. The cylindrical body 14 is formed of material such as diecast metal, with a tapered rear end closure 15 terminating in a central boss 16. The body must be formed of material of Suficient strength and density to withstand collapse under pressure and prevent infiltration of well bore fluid. Boss 16 is formed with a transverse bore 17, substantially normal to the axis of revolution of the body, to receive the Primacord 12. The Primacord 12 is threaded through the bores 17 in each of the charges 10 sequentially, and connected as described above to the detonating cap 13.

The forward end of each of the cylindrical body portions 14 is sealed by a frangible cover '19, or equivalent means, to prevent the entrance of well bore fluid. It'will be appreciated by those skilled in the art that well bore fluid must be kept out of the recessed portion of the shaped charge unit, since if foreign matter is present in this cavity, it may, upon detonation of the charge, interfere with or prevent the formation of a jet. Hence the cover 19 is formed of ceramic or other frangible material sufliciently strong in compression to resist well pressure, but readily shattered by the explosion of the charge into finely divided fragments. The cover 19 is so shaped as to provide an adequate standoff space ahead of the charge cavity for the proper formation of a jet, in accordance with principles well known in the art.

Within the cylindrical body 14 is disposed the explosive charge 20, which is shaped or hollowed to form a recess or cavity 21 with such a configuration as will produce the most efiicient jet for the desired purpose. A thin metal liner 22 formed preferably of copper, aluminum or the like, is shaped congruently with the inner surface of the shaped charge cavity 21. The liner 22 is applied snugly to that surface, and aids the jet in a manner well known to those familiar with shaped charges. A booster charge 24 is disposed adjacent the Primacord and in contact with the central, rearmost part of the main explosive charge 20.

With the embodiment shown in Figures 1 and 2, the central body portion 2 is sufficiently strong to withstand the shock of simultaneously firing all of the shaped charges 10. Since the body 2 does not attemptto contain these charges, and is not in the direct line of'fire, it is not shattered by the explosion. The Primacord and the shaped charge units themselves disintegrate completely on firing, as do the supporting straps 11. The gun body 2 remains attached to the cable and thereby may be removed from the borehole for successive reuses.

The embodiment shown in Figures 3a to 7 has the features mentioned above common to the several species of the invention, but accomplishes the result of leaving no debris in the hole by using a head portion and a strong, flexible steel cable to constitute the body. The body connects the charges to the cable head either directly or through an adapter. A relatively rigid structure is obtained by using a looped cable under tension to fix a plurality of shaped charges 10 in and between disintegrable spacers 30. The spacers 30 may be formed of Steatite or equivalent frangible ceramic material strong in compression, but reducible to fine powder by the explosion of the charges. Figures 3a and 3b are intended to be taken together to illustrate the gun generally denoted as 31. Figures 3 and 3b represent respectively the lower portions of the gun. The head portion 32 of gun 31 is arranged to be supported during running in and during removal by a conventional grappling or fishing tool. Alternatively, the head might be modified to permit detonation of the charges to be accomplished by a go-dev-il or similar device of conventional construction.

In the embodiment of Figures 3a to 7, the gun 31 is formed of steel or similar material in its upper portion,

including an adapter 33 and the head 32 for engagement with running-in and retrieving tools. The lower portion, generally indicated at 34, comprises the beforementioned series of shaped charges 10 mounted in and separated by spacers 30, and secured together by the tension member, which may be a looped steel cable 35. Cable 35 is anchored in the upper body of gun 3 1 by means such as set screws 36, which may conveniently be of the Allenhead type. The set screws 36 are tightened after the cable has been pulled taut in the side groves 37 formed in the spacers 30.

Each of the spacers 30 has formed in the upper and lower ends thereof a main half-round cylindrical recess 39 of radius such as to receive snugly the charge 10. In each of the spacers 30 a rear half-round recess 40 of lesser radius than the main recess 39 is provided. The angular face 43- connecting these recesses cooperates with the recesses 39 to define a seat for the charge 10, and to prevent movement of the charge toward the rear recesses 40. The rear recesses 40 of adjacent spacers cooperate to receive the boss 16, with its interlaced Primacord 12. The transverse dimensions of the recesses 39 and 49 are so coordinated that no one of the charges 10 will extend beyond the outer surface of the gun body 34 on either side, and the Primacord 12 assists in fixing the position of the charges in their seats.

A detonator fuse passage 41 extends diagonally through each spacer body to receive the Primacord 12. The sides of grooves 37 are formed in the body 30 of each spacer at an acute angle to radii thereof, and in assembly, adjacent spacers are aligned with their grooves 37 heading in opposite directions. This enables the outer lips 38 of the grooves 37 to partially enclose the cables 35 in overlapping or interlocking fashion, as best shown in Figure 5, while at the same time the detonator passages 41 enable the detonating fuse element to be operatively disposed relative to each of the charges 10 in sequence.

The detonating fuse itself'may be initiated by conventional means for applying current through the contact pin 42 seen in detail in Figure 4a. The current then passes through a conductor 44, which in turn delivers it to a blasting cap 45. These elements are suitably insulated from the body 31 and well bore fluid, the latter elements acting either together or separately as the return circuit to the source of electric current. In operation, the blasting cap 45 detonates a booster 46, which in turn detonates the detonating fuse 12, to fire the charges 10 substantially simultaneously. The lower end of the fuse 12 is suitably sealed at 47, as shown in Figure 4c, to prevent entry of well bore fluid. Such a seal may be made, for example, by taping and impregnating the Primacord end with a sealing compound.

It can be seen that each of the charges 10 will be detonated nearly simultaneously, perforating the well at the desired points, and reducing the spacers 30 to a fine powder which will not constitute objectionable debris. Thereafter the cable head 32 may be pulled from the well, taking with it all of the metal parts, including the steel cable. Because of the flexibility of this cable, the possibility of difficulty in removal of the suspended parts is minimized.

Due to the high compressive strength of the material of which the spacers 30 are made, it is possible to make up a string of 1%" outside diameter charges and spacers of the order of fifteen feet in length, yet sufficiently rigid so that it may be carried by the operator without buckling. This rigidity is a great practical convenience in operation, and yet it is obtained with structure which does not leave any material in the well of an objectionable nature.

Another embodiment, with several varying details of construction, is shown in Figures 8-11. Here the steel cable is omitted, and the charges and spacers are held together by a tension member consisting of a loop of the detonating fuse 50. This loop is also used, together with the usual detonating {fuse 12, for detonation purposes. The upper ends of the supporting loop of the fuse 50 and the upper end of the fuse 12, are all connected together at a joint 51 to permit imitation by a detonating cap 45. The joint 51 is suitably sealed against the effects of well bore fluid. The supporting fuse cord loop 50 is secured in place, after the cords have been drawn up tightly, by set screw means 36 similar to those shown in Figure 4b. Detonation of the fuse cord elements 12 and 50 will be initiated simultaneously, but the rapidity with which the detonating wave travels along the cord is such as to insure that complete initiation of all the charges will occur before the assembly has been blown apart. In these figures the head portion is not shown, but that of Figures 4a and 4b may be used, so that the upper portion 31 of the gun body may be removed intact from the borehole. There will be no material in addition thereto which requires removal.

An alternative constructional detail for use with the embodiment of Figure 8 is seen in Figure 10. Here the fuse cord loop 55 is not joined directly to the initiating fuse 12, but is merely held closely adjacent thereto in the body 31 by tying a stevedores knot 56, or the equivalent, in each of the upper ends of the fuse cord itself. With the more sensitive varieties of Primacord, such as PETN, a detonation wave will be initiated in each side of the fuse cord loop 55 by shock waves from the cord 12, assisted by the detonation of the successive shaped charges-10. Here again, the velocity of the detonation wave in the fuse cord is such that complete initiation of all the shaped charges will occur nearly simultaneously and before the lower charges and spacers can drop or be blown away a perceptible distance from the upper ones. In this figure another constructional detail contributing to ease and speed of assembly in the field has been illustrated. A tapering helical guide spring 57 is disposed about the lower end of booster section 59. This spring assists in guiding the upper end of the fuse cord section 12 into intimate contact with the booster, and urges it resiliently thereagainst, so that the taped or oherwise sealed joint shown at 51 in Figure 8 embodiment need not be used. If desired, however, after the advantages of speed in assembly have been utilized, the joint may be sealed or wrapped over the spring member.

Another alternative detail of construction for the upper portion of the embodiment of Figures 8-10 is shown in Figure 11. Here the fuse cord loop 59a is continuous at its upper portion 60 and the lower ends are joined as by 7 a conventional square knot 61 to maintain the assembly intact until firing.

It is contemplated that the shape of the spacers may also be so modified as to direct the charges in other desired orientation patterns as for example, all in the same direction, or in other azimuthal arrays.

It will be seen from the description above that improved means particularly effe ctive with shaped charges have been presented for accomplishing thru-tubing perforation.

What is claimed is:

1. In apparatus for perforating wells, the combination comprising: a plurality of separate, generally cylindrical spacer members, said spacer members having substantially equal diameters and being positioned in coaxial alignment, adjacent spacer members having opposed end faces abutting each other, said spacer members providing a pair of laterally spaced, longitudinal passages extending therethrough, said passages being on opposite sides of the axis of said spacer members; a pair of flexible tension members, one being received in each of said passages and engaging the end of the terminal spacer member; a head member coaxially aligned with and abutting the spacer member at one end of said plurality; means on said head member for securing said tension members to said head member and under tension to exert compression on the spacer members embraced between said headmember and the terminal spacer member, whereby to provide a substantially rigid assembly; said spacer members providing a plurality of laterally disposed, perforating unit receiving recesses longitudinally spaced therealong; shaped explosive charge perforating units, one mounted in each said recess to direct its perforating jet laterally from the apparatus; means for firing said perforating units; said spacer members being of frangible material reducible to fine powder by the explosion of the. charge units; and means for lowering the apparatus into a well.

2. In apparatus for perforating wells, the combination comprising: a plurality of separate, generally cylindrical spacer members, said spacer members having substantially equal diameters and being positioned in coaxial alignment, adjacent spacer members having opposed end faces abutting each other, said spacer members providing a pair of laterally spaced, longitudinal passagestextending therethrough, said passages being on opposite sides of the axis of said spacer members; a pair of flexible cable members, one being received in each of said passages and engaging the end of the terminal spacer member; a head member coaxially aligned with and abutting the spacer member at one end of said plurality; means on said head member for securing said flexible cable members to said head member and under tension to exert compression on the spacer members embraced between said head member and the terminal spacer member, whereby to provide a substantially rigid assembly; said spacer members providing a plurality of laterally disposed, perforating unit receiving recesses longitudinally spaced therealong, each said recess being formed by opposed cavities provided in the abutting faces of adjacent spacer members; shaped explosive charge perforating units, one mounted in each said recess to direct its perforating jet laterally from the apparatus; means for firing said perforating units; said spacer members being of frangible material reducible to fine powder by the explosion of the charge units; and means for lowering the apparatus into a well.

3. In apparatus for perforating wells, the combination comprising: a plurality of separate, generally cylindrical spacer members, said spacer members having substantially equal diameters and being positioned in coaxial alignment, adjacent spacer members having opposed end faces abutting each other, said spacer members :providing' a pair of laterally spaced, longitudinal passages extend"- ing therethrough, saidpassages being on opposite sides of the axis of said spacer members; a pair of flexible cable members, one being received in each of said passages and engaging the end of the terminal spacer member; a head member coaxially aligned with andabutting the spacer member at one end of said plurality; means on said head member for securing said flexible cable members to said head member and under tension to exert Compression on the spacer members embraced between said head member and the terminal spacer member, whereby to provide a substantially rigid assembly; said spacer members providing a plurality of laterally disposed, perforating unit receiving recesses longitudinally spaced therealong, each said recess being formed by opposed' cavities provided in the abutting faces of adjacent spacer members; shaped explosive charge perforating units, one mounted in each said recess to direct its perforating jet laterally from the apparatus; means for firing said perforating units, said firing means including longitudinal detonator fuse passage means in said spacer members, a length of detonator fuse in said passage means arranged in firing relation to said perforating units, and means for initiating said detonator fuse; said spacer members being 'of frangible 'material reducible to fine powder by the 'explosion'of the charge units; and means for lowering the apparatus into a well.

4. In apparatus for perforating wells, the combination comprising: a generally cylindrical head member for connection with means for running the apparatus into a well; a plurality of separate, generally cylindrical spacer members, said spacer members having substantially equal diamet'ers and being positioned in coaxial alignment with said head member, one of said spacer members having an end face abutting an opposed end face of said head member, adjacent spacer members having opposed end faces abutting each other, said spacer members providing a pair of laterally spaced, longitudinal grooves extending therealong, said grooves being on diametrically 0pposite sides of said spacer members; a loop of flexible steel cable, one end of said loop extending through one of said grooves and the other end of said loop extending through the other ofsaid grooves, the ends of said cable extending into said head member; means anchoring the ends of said cable in said head member under tension thereby applying the tension force of said cable to said head member and-to the distal spacer member of said plurality of spacer members to exert compression on the spacer members embraced between said head member and said distal spacer member to provide a substantially rigid assembly; said spacer members providing a plurality of laterally disposed, perforating unit receiving recesses longitudinally spaced therealong, each said recess being formed by opposed cavities provided in the abutting faces'of adjacent spacer members; shaped explosive charge perforating units, one mounted in each said recess to direct its perforating jet laterally from the apparatus; and means for firing said perforating units, said firing means including longitudinal detonator fuse passage means in said spacer members, a length of detonator fuse in said passage means arranged in firing relation to said perforating units, an end of said fuse extending into said head member, and an electric blasting cap in said head member in initiating relation to said end of said fuse; said spacer members being of frangible ceramic material reducible to fine powder by the explosion of'the charge units.

5. In apparatus for perforating wells, the combination comprising: a plurality of separate, generally cylindrical spacer members, said spacer members having substantially equal diameters and being positioned in coaxial alignment, adjacent spacer members having opposed end faces abutting each other, said spacer members providing a pair of laterally spaced, longitudinal passages extending therethrough, said passages being on opposite sides of the axis of said spacer members; a pair of flexible detonating fuse cord members, one being received in each of said passages and engaging the end of the terminal spacer member; a head member coaxially aligned with and abutting the spacer member at one end of said plurality; means on said head member for securing said detonating fuse cord members to said head member and under tension to exert compression on the spacer members embraced between said head member and the terminal spacer member, whereby to provide a substantially rigid assembly; said spacer members providing a plurality of laterally disposed, perforating unit receiving recesses longitudinally spaced therealong, each said recess being formed by opposed cavities provided in the abutting faces of adjacent spacer members; shaped explosive charge perforating units, one mounted in each said recess to direct its perforating jet laterally from the apparatus; means for firing said perforating units, said firing means including longitudinal detonator fuse passage means in said spacer members and a length of detonator fuse in said passage means arranged in firing relation to said 10 perforaing units; means for initiating said detonating fuse cord members and said detonator fuse; said spacer members being of frangible material reducible to fine powder by the explosion of said detonating fuse cord members, detonating fuse and charge units; and means for lowering the apparatus into a well.

References Cited in the file of this patent UNITED STATES PATENTS 

